I get what you’re trying to do here, but you realize it’s like asking for an automatic locking door to never automatically lock except for when you want it to automatically lock…
To *defeat* the more link you have to work around it, and that means replacing the_content()
with some other method of displaying post content. A quick way to do this is to echo $post->post_content, but this leaves out any formatting WordPress takes care of. So to do things right, you want to wrap the formatting/conversion functions around $post->post_content, like the following:
<?php
echo wptexturize(convert_smilies(convert_chars(wpautop($post->post_content))));
?>
Looks complicated, but takes care of (I believe all) the formatting features built into WordPress that act on post content.
Note this will bypass WordPress’ filtering API. If you have any plugins that work with post content, you would need to add their functions into that nested group above (ech).